A modified GaZSM-5 molecular sieve catalytic material, a preparation method and application thereof

Abstract

The present application relates to the technical field of propane aromatization reaction catalyst, and discloses a modified GaZSM-5 molecular sieve catalytic material, a preparation method and application thereof.The preparation method is as follows: GaZSM-5 molecular sieve is prepared by in-situ hydrothermal crystallization; a platinum precursor and a rare earth precursor are dissolved in deionized water to obtain a platinum-rare earth precursor solution; the GaZSM-5 molecular sieve is added into the platinum-rare earth precursor solution, and after ultrasonic oscillation, the product is ground, evaporated and calcined to obtain a platinum-rare earth dual-component modified modified GaZSM-5 molecular sieve catalytic material.The platinum species and the rare earth metal species are highly dispersed in the GaZSM-5 by the co-impregnation method, the platinum, the rare earth element and the skeleton Ga atom interact with each other, the dehydrogenation and aromatization active sites of the catalytic material are regulated, the aromatic hydrocarbon yield is improved, the deactivation caused by carbon deposition and platinum species sintering is relieved, and the cycle stability of the catalyst is improved.

Description

Technical Field

[0001] This invention relates to the field of propane aromatization reaction catalyst technology, and in particular to a modified GaZSM-5 molecular sieve catalytic material, its preparation method, and its application. Background Technology

[0002] Propane aromatization is an acid-catalyzed tandem reaction process, mainly involving propane dehydrogenation and olefin oligomerization, cyclization, and aromatization. Among numerous catalytic materials, MFI-type molecular sieves, represented by ZSM-5, have gradually become the most promising catalyst system for propane dehydrogenation aromatization due to their unique three-dimensional intersecting straight-channel structure with double ten-membered rings, tunable acid properties, and good shape-selective catalytic performance, which can provide suitable catalytic active sites.

[0003] Gallium (Ga) is a commonly used metal component in the propane aromatization process of ZSM-5 molecular sieves. The introduction of gallium can provide dehydrogenation active centers and effectively promote the synergistic effect of acid sites, thereby improving the yield of aromatics. Patent CN118356967A provides a Ga2O3@HZSM-5 catalyst for catalytic propane aromatization and its preparation method. By highly dispersing Ga2O3 on the surface and / or within the pores of HZSM-5, the synergistic effect of Ga sites and active sites of the molecular sieve is promoted. When the reaction time is as long as 60 min, the yield of BTX in the product can reach 28%.

[0004] Platinum (Pt), a precious metal, possesses highly efficient dehydrogenation capabilities. In propane aromatization, Pt can serve as a dehydrogenation active center, effectively promoting propane activation and lowering the energy barrier for propane conversion. Xiang et al. (Appl. Catal. A-Gen., 2023, 665, 119368) shifted the propane conversion pathway from the cracking reaction dominated by pure HZSM-5 to the dehydrogenation aromatization pathway by introducing a very low loading of Pt (500 ppm) into ZSM-5. Compared to pure HZSM-5, the propane conversion rate of 500 ppm Pt / ZSM-5 under the same conditions was increased by 3.38 times, and the BTX selectivity was also improved to 40%. Wang et al. (Catal. Sci. Technol., 2022, 12, 7281) utilized Pt's extremely strong CH activation ability to overcome the limitations of insufficient dehydrogenation activity in traditional catalysts. They confined a Pt-Zn alloy within a ZSM-5 molecular sieve, and the resulting 0.7Pt-1Zn@HZSM-5 catalyst achieved a propane conversion of 74% and an aromatic selectivity of 56% at 550 °C, significantly higher than the catalytic performance of traditional Zn / ZSM-5 and Ga / ZSM-5 (conversion rate of approximately 34%) reported in the literature.

[0005] In summary, while introducing Ga or Pt into ZSM-5 can significantly improve catalytic performance, under traditional loading methods, Ga species tend to aggregate on the outer surface of the molecular sieve as Ga2O3, resulting in insufficient synergistic effect with acid sites and low overall efficiency of dehydrogenation and aromatization. Furthermore, the high activity of Pt not only easily triggers severe cracking side reactions, but Pt also readily undergoes sintering in high-temperature reaction atmospheres, further accelerating catalyst deactivation. Summary of the Invention

[0006] This invention aims to overcome the aforementioned problems in the prior art by providing a platinum-rare earth dual-component modified GaZSM-5 molecular sieve catalytic material, its preparation method, and its application. Through a co-impregnation method, platinum species and rare earth metal species are highly dispersed in GaZSM-5. Platinum provides active sites for propane dehydrogenation, while rare earth elements stabilize the platinum nanoparticles, preventing high-temperature sintering. The interaction between platinum, rare earth elements, and the framework Ga atoms regulates the dehydrogenation and aromatization active sites of the catalytic material, improving the yield of aromatic hydrocarbons. Simultaneously, it alleviates deactivation caused by carbon deposition and platinum species sintering, enhancing the catalyst's cycle stability.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing a modified GaZSM-5 molecular sieve catalytic material, comprising the following steps: (1) GaZSM-5 molecular sieve was prepared by in-situ hydrothermal crystallization. (2) Dissolve the platinum precursor and rare earth precursor in deionized water to obtain a platinum-rare earth precursor solution; (3) Add GaZSM-5 molecular sieve to platinum-rare earth precursor solution, and after ultrasonic vibration, grind, evaporate and calcine the product to obtain platinum-rare earth two-component modified GaZSM-5 molecular sieve catalyst material.

[0008] In the propane aromatization process catalyzed by Ga / ZSM-5, Ga species introduced through conventional methods mainly aggregate on the outer surface of the molecular sieve as Ga2O3, providing Lewis acid sites to promote propane activation. However, the spatial distribution of these outer surface Lewis acid sites and the inherent Brønsted acid sites inside the molecular sieve is uneven, resulting in insufficient synergy and a low overall efficiency of dehydrogenation and aromatization. Furthermore, excessively strong Brønsted acid sites in the molecular sieve are prone to triggering severe cracking side reactions, generating large amounts of dry gas, thus significantly reducing the selectivity of the target aromatic product. To address the limitations of Ga / ZSM-5, this invention introduces Ga species into the molecular sieve framework to regulate the local microenvironment of the active sites. Since Ga and Al both belong to Group IIIA elements, Ga... 3+ The ionic radius (approximately 0.062 nm) is similar to that of Al. 3+The nanoparticles (approximately 0.0535 nm) are similar, and both are +3 valence, tending towards tetrahedral coordination. Under hydrothermal synthesis conditions, Ga... 3+ Al in the framework can be replaced by forming Si-O(H)-Ga bonds. 3+ or Si 4+ The Ga species introduced into the framework has a unique coordination environment, which not only serves as a potential Lewis acid site to assist in dehydrogenation, but also provides a milder Brønsted acid site than Si-O(H)-Al for the formation of the Si-O(H)-Ga structure, thereby inhibiting the occurrence of side reactions.

[0009] Based on the GaZSM-5 framework, a second metal is still needed to provide the main dehydrogenation sites and compensate for the insufficient dehydrogenation activity of the Ga sites in the framework. Platinum (Pt) has a very strong ability to dissociate CH bonds and is a commonly used metal component in propane dehydrogenation. However, Pt is prone to Oswald ripening under high-temperature reaction atmospheres, leading to metal species migration and sintering, which severely weakens the stability of the catalyst. At the same time, Pt also has a strong ability to crack C-C bonds, which will catalyze the cracking reaction of propane and reaction intermediates during the reaction to generate a large amount of worthless methane and ethane, which seriously reduces carbon atom utilization and the selectivity of the target product. Therefore, it is necessary to introduce an auxiliary agent to modify the Pt species. Rare earth metals, represented by lanthanides, can not only improve the dispersion of Pt on the support and increase the density of active sites, but also anchor Pt nanoparticles through strong metal-support interaction (SMSI), inhibiting Pt migration and agglomeration at high temperatures and effectively alleviating sintering deactivation. Meanwhile, rare earth elements can use 4f electrons to regulate the d-band center of Pt, increase the electron density of Pt, thereby weakening Pt's ability to break C-C bonds and inhibiting the occurrence of cracking side reactions.

[0010] Therefore, this invention utilizes in-situ hydrothermal synthesis technology to introduce Ga species into the framework of silica-alumina molecular sieves, and employs a co-impregnation method to load platinum and rare earth elements onto the molecular sieves. By controlling the conditions of the hydrothermal synthesis process and the co-impregnation process, the catalyst exhibits efficient and stable catalytic performance.

[0011] As a preferred option, the modified GaZSM-5 molecular sieve catalytic material has a platinum loading of 0.1-1.0 wt% and a rare earth loading of 0.1-1.0 wt%.

[0012] As a preferred option, the steps for preparing GaZSM-5 molecular sieve by in-situ hydrothermal crystallization in step (1) are as follows: mixing silicon source, aluminum source, gallium source, template agent and deionized water, stirring evenly to obtain a mixture; transferring the mixture to a closed reactor for hydrothermal crystallization reaction; the product after crystallization reaction is centrifuged, washed and dried, and then calcined in an air atmosphere to obtain GaZSM-5 molecular sieve.

[0013] Preferably, the silicon source is tetraethyl orthosilicate; the aluminum source is boehmite; the gallium source is gallium nitrate hydrate and / or gallium chloride; the template agent is tetrapropylammonium hydroxide; the molar ratio of silicon source, aluminum source, gallium source, template agent and deionized water is 1:0.01~0.02:0.008~0.009:0.3~0.5:40~50; wherein, the amount of silicon source is SiO2, the amount of aluminum source is Al2O3, and the amount of gallium source is Ga2O3.

[0014] Preferably, the hydrothermal crystallization reaction is carried out at a temperature of 170~190℃ for 60~90h; during calcination, the temperature is first raised from room temperature to 350~450℃ at a rate of 1~2℃ / min, and then raised to 500~600℃ at a rate of 0.5~0.8℃ / min for calcination for 4~6h.

[0015] Preferably, the platinum precursor in step (2) includes chloroplatinic acid hydrate and / or tetraammineplatinum nitrate; the rare earth precursor includes one or more of lanthanum nitrate hexahydrate, cerium nitrate hexahydrate, praseodymium nitrate hexahydrate, neodymium nitrate hexahydrate, and yttrium nitrate hexahydrate.

[0016] As a preferred option, the grinding and evaporation conditions in step (3) are as follows: the product after ultrasonic vibration is fully ground at 100~140℃ until it is completely evaporated into a solid; the calcination conditions are as follows: the temperature is raised from room temperature to 500~600℃ at a rate of 0.5~0.8℃ / min in air and calcined for 4 h.

[0017] Secondly, the present invention provides a modified GaZSM-5 molecular sieve catalytic material prepared by the above preparation method.

[0018] Thirdly, the present invention provides an application of the above-mentioned modified GaZSM-5 molecular sieve catalytic material in the propane aromatization reaction. The method is as follows: the modified GaZSM-5 molecular sieve catalytic material is first pretreated with hydrogen at the reaction temperature, then purged with nitrogen at the same temperature, and then the raw material gas is introduced to carry out the reaction. The reaction temperature is 500~600℃ and the reaction pressure is atmospheric pressure.

[0019] Preferably, the feed gas is a propane / nitrogen mixture, in which the volume content of propane is 35-45%.

[0020] Therefore, the present invention has the following beneficial effects: (1) This invention first constructs Ga species in the ZSM-5 molecular sieve framework through in-situ hydrothermal synthesis technology, which optimizes the distribution of acid sites in the molecular sieve and enhances the synergistic effect between active sites. Secondly, platinum species and rare earth metal species are introduced by co-impregnation method. The platinum species effectively improves the dehydrogenation activity and propane conversion ability of the catalyst, while the rare earth metal species significantly inhibit the high-temperature sintering deactivation of the platinum species through anchoring, dispersion regulation and electronic structure modification, thereby greatly extending the service life of the catalyst. (2) The catalytic material of the present invention has the advantages of good catalytic activity, high yield of aromatic products, and excellent stability. The yield of aromatics is not less than 50% within 9 hours of reaction, and the cumulative cycle regeneration life of the catalyst can exceed 1000 hours, which has good cycle regeneration performance. Attached Figure Description

[0021] Figure 1 These are X-ray powder diffraction patterns of the catalytic materials obtained in Examples 1, 4, 14, 1, 5, and 6 of this invention.

[0022] Figure 2 This is a TEM image of the catalytic material obtained in Example 1 of the present invention before the reaction.

[0023] Figure 3 This is a TEM image of the catalytic material obtained in Example 4 of the present invention before the reaction.

[0024] Figure 4 This is a TEM image of the catalytic material obtained in Example 14 of the present invention before the reaction.

[0025] Figure 5 This is a TEM image of the catalytic material obtained in Comparative Example 1 of this invention before the reaction.

[0026] Figure 6 This is a TEM image of the catalyst material obtained in Comparative Example 5 of this invention before the reaction.

[0027] Figure 7 This is a TEM image of the catalyst material obtained in Comparative Example 6 of this invention before the reaction.

[0028] Figure 8 This is a TEM image of the catalytic material obtained in Example 4 of this invention after reacting for 12 hours.

[0029] Figure 9 This is a TEM image of the catalytic material obtained in Comparative Example 1 of this invention after reacting for 12 hours.

[0030] Figure 10 This is a TEM image of the catalyst material obtained in Comparative Example 5 of this invention after reacting for 12 hours.

[0031] Figure 11This is a TEM image of the catalyst material obtained in Comparative Example 6 of this invention after reacting for 12 hours.

[0032] Figure 12 The catalyst material obtained in Example 23 of this invention was subjected to a temperature of 550°C for 0.8 hours. -1 Performance graph of long-term lifetime testing under mass space velocity reaction conditions.

[0033] Figure 13 The catalyst material obtained in Comparative Example 1 of this invention was subjected to a temperature of 550°C for 0.8 hours. -1 Performance graph of long-term lifetime testing under mass space velocity reaction conditions.

[0034] Figure 14 The catalyst material obtained in Comparative Example 5 of this invention was subjected to a temperature of 550°C for 0.8 hours. -1 Performance graph of long-term lifetime testing under mass space velocity reaction conditions.

[0035] Figure 15 The catalyst material obtained in Comparative Example 6 of this invention was subjected to a temperature of 550°C for 0.8 hours. -1 Performance graph of long-term lifetime testing under mass space velocity reaction conditions. Detailed Implementation

[0036] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0037] In this invention, unless otherwise specified, all equipment and raw materials are available from the market or commonly used in the industry. Unless otherwise specified, the methods in the following embodiments are conventional methods in the art.

[0038] General Implementation Examples: A method for preparing a modified GaZSM-5 molecular sieve catalytic material includes the following steps: (1) GaZSM-5 molecular sieve was prepared by in-situ hydrothermal crystallization. (2) Dissolve the platinum precursor and rare earth precursor in deionized water to obtain a platinum-rare earth precursor solution; (3) Add GaZSM-5 molecular sieve to platinum-rare earth precursor solution, and after ultrasonic vibration, grind, evaporate and calcine the product to obtain platinum-rare earth two-component modified GaZSM-5 molecular sieve catalyst material.

[0039] In one specific implementation, the modified GaZSM-5 molecular sieve catalytic material has a platinum loading of 0.1-1.0 wt% and a rare earth loading of 0.1-1.0 wt%.

[0040] As a specific implementation method, the steps of preparing GaZSM-5 molecular sieve by in-situ hydrothermal crystallization in step (1) are as follows: mixing silicon source, aluminum source, gallium source, template agent and deionized water, stirring evenly to obtain a mixture; transferring the mixture to a closed reactor for hydrothermal crystallization reaction; the product after crystallization reaction is centrifuged, washed and dried, and then calcined in an air atmosphere to obtain GaZSM-5 molecular sieve.

[0041] In one specific embodiment, the silicon source is tetraethyl orthosilicate; the aluminum source is boehmite; the gallium source is gallium nitrate hydrate and / or gallium chloride; the template agent is tetrapropylammonium hydroxide; the molar ratio of silicon source, aluminum source, gallium source, template agent and deionized water is 1:0.01~0.02:0.008~0.009:0.3~0.5:40~50; wherein, the amount of silicon source is SiO2, the amount of aluminum source is Al2O3, and the amount of gallium source is Ga2O3.

[0042] In one specific implementation, the hydrothermal crystallization reaction is carried out at a temperature of 170~190℃ for 60~90h; during calcination, the temperature is first raised from room temperature to 350~450℃ at a rate of 1~2℃ / min, and then raised to 500~600℃ at a rate of 0.5~0.8℃ / min for calcination for 4~6h.

[0043] In one specific implementation, the platinum precursor in step (2) includes chloroplatinic acid hydrate and / or tetraammineplatinum nitrate; the rare earth precursor includes one or more of lanthanum nitrate hexahydrate, cerium nitrate hexahydrate, praseodymium nitrate hexahydrate, neodymium nitrate hexahydrate, and yttrium nitrate hexahydrate.

[0044] As a specific implementation, the grinding and evaporation conditions in step (3) are: the product after ultrasonic vibration is fully ground at 100~140℃ until it is completely evaporated into a solid; the calcination conditions are: the temperature is raised from room temperature to 500~600℃ at a rate of 0.5~0.8℃ / min in air and calcined for 4 h.

[0045] Example 1:

[0046] A method for preparing a platinum-rare earth two-component modified GaZSM-5 molecular sieve catalytic material, comprising the following steps: (1) Synthesis of molecular sieves by in-situ hydrothermal crystallization: 12 g of tetrapropylammonium hydroxide (40 wt.%) was mixed with 40.12 g of deionized water and stirred at room temperature for 1 h to obtain mixed solution A. 268 mg of gallium(III) nitrate hydrate, 130.4 mg of boehmite, and 5 g of deionized water were mixed and stirred until fully dissolved, then added to mixed solution A and stirred for 2 h to obtain mixed solution B. 13.08 g of tetraethyl silicate was added dropwise to mixed solution B and stirred for 6 h to obtain mixed solution C. Mixed solution C was then transferred to a hydrothermal reactor and subjected to hydrothermal crystallization at 180 °C for 72 h. Finally, the obtained crystallized product was centrifuged, washed, and dried sequentially. The temperature was then increased from room temperature to 400 °C in air at a rate of 1 °C / min, followed by increasing the temperature to 550 °C at a rate of 0.5 °C / min and calcined at 550 °C for 5 h to obtain GaZSM-5 molecular sieve.

[0047] (2) Platinum species and rare earth species loaded by equal volume impregnation method The GaZSM-5 molecular sieve obtained in step (1) was impregnated with a mixed aqueous solution of chloroplatinic acid and lanthanum nitrate in equal volumes: 1 g of GaZSM-5 molecular sieve was mixed with 2 mL of the mixed aqueous solution of chloroplatinic acid and lanthanum nitrate in a centrifuge tube and ultrasonically vibrated for 1 h. The mass ratio of platinum to GaZSM-5 in the mixed solution was 0.001:1, and the mass ratio of lanthanum to GaZSM-5 was 0.001:1. After vibration, the mixture was transferred to an evaporating dish and ground at 120 °C until completely evaporated. The solid obtained after grinding was heated in air at a rate of 0.8 °C / min from room temperature to 550 °C and calcined at 550 °C for 4 h to obtain a platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst material, denoted as 0.1Pt0.1La / GaZSM-5.

[0048] Example 2:

[0049] The difference between Example 2 and Example 1 is that the mass ratio of lanthanum to GaZSM-5 in the mixed solution in step (2) is 0.005:1, and the resulting platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst is denoted as 0.1Pt0.5La / GaZSM-5.

[0050] Example 3:

[0051] The difference between Example 3 and Example 1 is that the mass ratio of platinum to GaZSM-5 in the mixed solution in step (2) is 0.005:1, and the resulting platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst is denoted as 0.5Pt0.1La / GaZSM-5.

[0052] Example 4:

[0053] The difference between Example 4 and Example 1 is that the mass ratio of platinum to GaZSM-5 in the mixed solution in step (2) is 0.005:1, and the mass ratio of lanthanum to GaZSM-5 is 0.005:1. The resulting platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst is denoted as 0.5Pt0.5La / GaZSM-5.

[0054] Example 5:

[0055] The difference between Example 5 and Example 1 is that the mass ratio of platinum to GaZSM-5 in the mixed solution in step (2) is 0.005:1, and the mass ratio of lanthanum to GaZSM-5 is 0.01:1. The resulting platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst is denoted as 0.5Pt1.0La / GaZSM-5.

[0056] Example 6:

[0057] The difference between Example 6 and Example 1 is that the mass ratio of platinum to GaZSM-5 in the mixed solution in step (2) is 0.01:1, and the mass ratio of lanthanum to GaZSM-5 is 0.005:1. The resulting platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst is denoted as 1.0Pt0.5La / GaZSM-5.

[0058] Example 7:

[0059] The difference between Example 7 and Example 1 is that the mass ratio of platinum to GaZSM-5 in the mixed solution in step (2) is 0.01:1, and the mass ratio of lanthanum to GaZSM-5 is 0.01:1. The resulting platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst is denoted as 1.0Pt1.0La / GaZSM-5.

[0060] Example 8:

[0061] The difference between Example 8 and Example 1 is that the gallium source added in step (1) is replaced with gallium chloride, the mass of gallium chloride is 184.2 mg, and the molar ratio of silicon to gallium in the synthesized GaZSM-5 molecular sieve is 60. In step (2), the mass ratio of platinum to GaZSM-5 in the mixed solution is 0.005:1, the mass ratio of lanthanum to GaZSM-5 is 0.005:1, and the resulting platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst is denoted as 0.5Pt0.5La / GaZSM-5(GaCl3).

[0062] Example 9:

[0063] The difference between Example 9 and Example 1 is that in step (1), 12 g of tetrapropylammonium hydroxide (40 wt.%), 130.4 mg of boehmite, and 40.12 g of deionized water were mixed and stirred at room temperature for 1 h to obtain mixed solution A; 268 mg of gallium(III) nitrate hydrate was mixed with 5 g of deionized water, stirred until completely dissolved, and then added to mixed solution A and stirred for 2 h to obtain mixed solution B; the subsequent steps were the same as step (1) of Example 1. In step (2), the mass ratio of platinum to GaZSM-5 in the mixed solution was 0.005:1, and the mass ratio of lanthanum to GaZSM-5 was 0.005:1. The resulting platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst was denoted as 0.5Pt0.5La / GaZSM-5.

[0064] Example 10:

[0065] The difference between Example 10 and Example 1 is that the crystallized product obtained in step (1) was centrifuged, washed, and dried in sequence, and then heated from room temperature to 400 ℃ in air at a rate of 1 ℃ / min, and then heated to 550 ℃ at a rate of 0.8 ℃ / min and calcined at 550 ℃ for 5 h; in step (2), the mass ratio of platinum to GaZSM-5 in the mixed solution was 0.005 : 1, and the mass ratio of lanthanum to GaZSM-5 was 0.005 : 1. The obtained platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst was denoted as 0.5Pt0.5La / GaZSM-5.

[0066] Example 11:

[0067] The difference between Example 11 and Example 1 is that the rare earth species in the mixed solution in step (2) is cerium, the mass ratio of platinum to GaZSM-5 is 0.005:1, the mass ratio of cerium to GaZSM-5 is 0.005:1, and the obtained platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst is denoted as 0.5Pt0.5Ce / GaZSM-5.

[0068] Example 12:

[0069] The difference between Example 12 and Example 1 is that the rare earth species in the mixed solution in step (2) is praseodymium, the mass ratio of platinum to GaZSM-5 is 0.005:1, the mass ratio of praseodymium to GaZSM-5 is 0.005:1, and the obtained platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst is denoted as 0.5Pt0.5Pr / GaZSM-5.

[0070] Example 13:

[0071] The difference between Example 13 and Example 1 is that the rare earth species in the mixed solution in step (2) is neodymium, the mass ratio of platinum to GaZSM-5 is 0.005:1, the mass ratio of neodymium to GaZSM-5 is 0.005:1, and the obtained platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst is denoted as 0.5Pt0.5Nd / GaZSM-5.

[0072] Example 14:

[0073] The difference between Example 14 and Example 1 is that the rare earth species in the mixed solution in step (2) is yttrium, the mass ratio of platinum to GaZSM-5 is 0.005:1, the mass ratio of yttrium to GaZSM-5 is 0.005:1, and the obtained platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst is denoted as 0.5Pt0.5Y / GaZSM-5.

[0074] Example 15:

[0075] The difference between Example 15 and Example 1 is that the platinum precursor in the mixed solution in step (2) is tetraammineplatinum(II) nitrate, the mass ratio of platinum to GaZSM-5 is 0.005:1, the mass ratio of lanthanum to GaZSM-5 is 0.005:1, and the obtained platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst is denoted as 0.5Pt0.5La / GaZSM-5(Pt(NH3)4(NO3)2).

[0076] Example 16:

[0077] The difference between Example 16 and Example 1 is that the mass ratio of platinum to GaZSM-5 in the mixed solution in step (2) is 0.005:1, the mass ratio of lanthanum to GaZSM-5 is 0.005:1, and the grinding and evaporation temperature is 100 °C. The obtained platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst is denoted as 0.5Pt0.5La / GaZSM-5.

[0078] Example 17:

[0079] The difference between Example 17 and Example 1 is that the mass ratio of platinum to GaZSM-5 in the mixed solution in step (2) is 0.005:1, the mass ratio of lanthanum to GaZSM-5 is 0.005:1, and the grinding and evaporation temperature is 140 °C. The obtained platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst is denoted as 0.5Pt0.5La / GaZSM-5.

[0080] Example 18:

[0081] The difference between Example 18 and Example 1 is that the mass ratio of platinum to GaZSM-5 in the mixed solution in step (2) is 0.005:1, and the mass ratio of lanthanum to GaZSM-5 is 0.005:1. The solid obtained after grinding is heated from room temperature to 550 °C in air at a rate of 0.5 °C / min. The obtained platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst is denoted as 0.5Pt0.5La / GaZSM-5.

[0082] Example 19:

[0083] The difference between Example 19 and Example 1 is that in step (2), the mass ratio of platinum to GaZSM-5 in the mixed solution is 0.005:1, and the mass ratio of lanthanum to GaZSM-5 is 0.005:1. The resulting platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst is denoted as 0.5Pt0.5La / GaZSM-5. In the application step, the reaction temperature is 600 ℃.

[0084] Example 20:

[0085] The difference between Example 20 and Example 1 is that the mass ratio of platinum to GaZSM-5 in the mixed solution in step (2) is 0.005:1, the mass ratio of lanthanum to GaZSM-5 is 0.005:1, and the resulting platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst is denoted as 0.5Pt0.5La / GaZSM-5; in the application step, the reaction temperature is 575 ℃.

[0086] Example 21:

[0087] The difference between Example 21 and Example 1 is that the mass ratio of platinum to GaZSM-5 in the mixed solution in step (2) is 0.005:1, the mass ratio of lanthanum to GaZSM-5 is 0.005:1, and the resulting platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst is denoted as 0.5Pt0.5La / GaZSM-5; in the application step, the reaction temperature is 525 ℃.

[0088] Example 22:

[0089] The difference between Example 22 and Example 1 is that the mass ratio of platinum to GaZSM-5 in the mixed solution in step (2) is 0.005:1, the mass ratio of lanthanum to GaZSM-5 is 0.005:1, and the resulting platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst is denoted as 0.5Pt0.5La / GaZSM-5; in the application step, the reaction temperature is 500 ℃.

[0090] Example 23:

[0091] The difference between Example 23 and Example 1 is that the mass ratio of platinum to GaZSM-5 in the mixed solution in step (2) is 0.005:1, and the mass ratio of lanthanum to GaZSM-5 is 0.005:1. The resulting platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst is denoted as 0.5Pt0.5La / GaZSM-5. A long-term lifetime test was conducted on the catalyst at a reaction temperature of 550 °C and a mass hourly space velocity (HHSV) of 0.8 h. -1 The reaction is paused when it reaches a certain point, and air is switched on (20 mL / min). -1 The atmosphere was calcined at 600 °C for 2 hours, then cooled to 550 °C for re-pretreatment and reaction, and this cycle was repeated several times.

[0092] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that no lanthanum was added to the mixed solution in step (2) (only platinum was impregnated), the mass ratio of platinum to GaZSM-5 was 0.005:1, and the resulting molecular sieve catalyst was denoted as 0.5Pt / GaZSM-5.

[0093] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that no platinum was added to the mixed solution in step (2) (only lanthanum was impregnated), the mass ratio of lanthanum to GaZSM-5 was 0.005:1, and the resulting molecular sieve catalyst was denoted as 0.5La / GaZSM-5.

[0094] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that GaZSM-5 catalyst material was used, which was not loaded with metal and is referred to as GaZSM-5.

[0095] Comparative Example 4: The difference between Comparative Example 4 and Example 1 is that Pt, Ga, and La were co-impregnated onto ordinary ZSM-5 molecular sieve (ZSM-5) using an impregnation method. The gallium loading was the same as in Example 1, and the mass ratio of platinum to ordinary ZSM-5 was 0.005:1, as was the mass ratio of lanthanum to ordinary ZSM-5. The preparation method of ordinary ZSM-5 was the same as that of GaZSM-5, except that the step of adding the gallium source was omitted. The resulting molecular sieve catalyst was designated as 0.5Pt0.5LaGa / ZSM-5.

[0096] Comparative Example 5: The difference between Comparative Example 5 and Example 1 is that platinum was impregnated onto ordinary ZSM-5 molecular sieve (ZSM-5) using an impregnation method, with a mass ratio of platinum to ordinary ZSM-5 of 0.005:1. The resulting molecular sieve catalyst is denoted as 0.5Pt / ZSM-5.

[0097] Comparative Example 6: The difference between Comparative Example 6 and Example 1 is that platinum and lanthanum were co-impregnated onto ordinary ZSM-5 molecular sieve (ZSM-5) using an impregnation method. The mass ratio of platinum to ordinary ZSM-5 was 0.005:1, and the mass ratio of lanthanum to ordinary ZSM-5 was 0.005:1. The resulting molecular sieve catalyst is designated as 0.5Pt0.5La / ZSM-5.

[0098] Comparative Example 7: The difference between Comparative Example 7 and Comparative Example 3 is that ZSM-5 molecular sieve catalytic material was used, which was not loaded with metal and is referred to as ZSM-5.

[0099] Comparative Example 8: The difference between Comparative Example 8 and Example 1 is that the mass ratio of platinum to GaZSM-5 in the mixed solution in step (2) is 0.005:1, and the mass ratio of lanthanum to GaZSM-5 is 0.02:1. The resulting platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst is denoted as 0.5Pt2.0La / GaZSM-5.

[0100] Comparative Example 9: The difference between Comparative Example 9 and Example 1 is that the mass ratio of platinum to GaZSM-5 in the mixed solution in step (2) is 0.02:1, and the mass ratio of lanthanum to GaZSM-5 is 0.005:1. The resulting platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst is denoted as 2.0Pt0.5La / GaZSM-5.

[0101] Comparative Example 10: The difference between Comparative Example 10 and Example 1 is that in step (1), 12 g of tetrapropylammonium hydroxide (40 wt.%), 130.4 mg of boehmite, and 40.12 g of deionized water were mixed and stirred at room temperature for 1 h to obtain mixed solution A; 13.08 g of tetraethyl silicate was added dropwise to mixed solution A and stirred for 6 h to obtain mixed solution B; 268 mg of gallium(III) nitrate hydrate was mixed with 5 g of deionized water, stirred until completely dissolved, and then added to mixed solution B and stirred for 2 h to obtain mixed solution C; the subsequent steps were the same as step (1) of Example 1. In step (2), the mass ratio of platinum to GaZSM-5 in the mixed solution was 0.005:1, and the mass ratio of lanthanum to GaZSM-5 was 0.005:1. The resulting platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst was denoted as 0.5Pt0.5La / GaZSM-5.

[0102] Comparative Example 11: The difference between Comparative Example 11 and Example 1 is that the crystallized product obtained in step (1) was centrifuged, washed, and dried in sequence, and then heated from room temperature to 400 °C at a rate of 1 °C / min in air, and then heated to 560 °C at a rate of 0.5 °C / min, and calcined at 560 °C for 5 h; in step (2), the mass ratio of platinum to GaZSM-5 in the mixed solution was 0.005:1, and the mass ratio of lanthanum to GaZSM-5 was 0.005:1. The obtained platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst was denoted as 0.5Pt0.5La / GaZSM-5.

[0103] Comparative Example 12: The difference between Comparative Example 12 and Example 1 is that the crystallized product obtained in step (1) was centrifuged, washed, dried, heated from room temperature to 550 ℃ in air at a rate of 1.2 ℃ / min, and calcined at 550 ℃ for 5 h; in step (2), the mass ratio of platinum to GaZSM-5 in the mixed solution was 0.005:1, and the mass ratio of lanthanum to GaZSM-5 was 0.005:1. The obtained platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst was denoted as 0.5Pt0.5La / GaZSM-5.

[0104] Comparative Example 13: The difference between Comparative Example 13 and Example 1 is that the crystallized product obtained in step (1) was centrifuged, washed, and dried in sequence, and then heated from room temperature to 400 ℃ in air at a rate of 1 ℃ / min, and then heated to 550 ℃ at a rate of 0.25 ℃ / min, and calcined at 550 ℃ for 5 h; in step (2), the mass ratio of platinum to GaZSM-5 in the mixed solution was 0.005 : 1, and the mass ratio of lanthanum to GaZSM-5 was 0.005 : 1. The obtained platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst was denoted as 0.5Pt0.5La / GaZSM-5.

[0105] Comparative Example 14: The difference between Comparative Example 14 and Example 1 is that in step (2), platinum and lanthanum were impregnated twice, with platinum impregnated first and then lanthanum impregnated. 1 g of GaZSM-5 molecular sieve was mixed with 2 mL of chloroplatinic acid aqueous solution in a centrifuge tube and ultrasonically vibrated for 1 h. The mass ratio of platinum to GaZSM-5 in the solution was 0.005:1. After vibration, the mixture was transferred to an evaporating dish and ground at 120 °C until completely evaporated. The solid obtained after grinding was heated in air at a rate of 0.8 °C / min from room temperature to 550 °C and calcined at 550 °C for 4 h. The calcined product was mixed with 2 mL of lanthanum nitrate aqueous solution in a centrifuge tube and ultrasonically vibrated for 1 h. The mass ratio of lanthanum to GaZSM-5 in the solution was 0.005:1. After shaking, the mixture was transferred to an evaporating dish and ground at 120 °C until completely dry. The resulting solid was then heated in air at a rate of 0.8 °C / min from room temperature to 550 °C and calcined at 550 °C for 4 h. The resulting platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst was designated as 0.5Pt / 0.5La / GaZSM-5.

[0106] Comparative Example 15: The difference between Comparative Example 15 and Example 1 is that in step (2), platinum and lanthanum were impregnated twice, with lanthanum impregnated first and then platinum impregnated. 1 g of GaZSM-5 molecular sieve was mixed with 2 mL of lanthanum nitrate aqueous solution in a centrifuge tube and ultrasonically vibrated for 1 h. The mass ratio of lanthanum to GaZSM-5 in the solution was 0.005:1. After vibration, the mixture was transferred to an evaporating dish and ground at 120 °C until completely evaporated. The solid obtained after grinding was heated in air at a rate of 0.8 °C / min from room temperature to 550 °C and calcined at 550 °C for 4 h. The calcined product was mixed with 2 mL of chloroplatinic acid aqueous solution in a centrifuge tube and ultrasonically vibrated for 1 h. The mass ratio of platinum to GaZSM-5 in the solution was 0.005:1. After shaking, the mixture was transferred to an evaporating dish and ground at 120 °C until completely dry. The resulting solid was then heated in air at a rate of 0.8 °C / min from room temperature to 550 °C and calcined at 550 °C for 4 h. The resulting platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst was designated as 0.5La / 0.5Pt / GaZSM-5.

[0107] Comparative Example 16: The difference between Comparative Example 16 and Example 1 is that the mass ratio of platinum to GaZSM-5 in the mixed solution in step (2) is 0.005:1, the mass ratio of lanthanum to GaZSM-5 is 0.005:1, and the grinding and evaporation temperature is 80 °C. The obtained platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst is denoted as 0.5Pt0.5La / GaZSM-5.

[0108] Comparative Example 17: The difference between Comparative Example 17 and Example 1 is that the mass ratio of platinum to GaZSM-5 in the mixed solution in step (2) is 0.005:1, the mass ratio of lanthanum to GaZSM-5 is 0.005:1, and the grinding and evaporation temperature is 160 °C. The obtained platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst is denoted as 0.5Pt0.5La / GaZSM-5.

[0109] Comparative Example 18: The difference between Comparative Example 18 and Example 1 is that the mass ratio of platinum to GaZSM-5 in the mixed solution in step (2) is 0.005:1, and the mass ratio of lanthanum to GaZSM-5 is 0.005:1. The solid obtained after grinding is heated from room temperature to 550 °C in air at a rate of 0.25 °C / min. The obtained platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst is denoted as 0.5Pt0.5La / GaZSM-5.

[0110] Comparative Example 19: The difference between Comparative Example 19 and Example 1 is that the mass ratio of platinum to GaZSM-5 in the mixed solution in step (2) is 0.005:1, and the mass ratio of lanthanum to GaZSM-5 is 0.005:1. The solid obtained after grinding is heated from room temperature to 550 °C in air at a rate of 1.2 °C / min. The obtained platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst is denoted as 0.5Pt0.5La / GaZSM-5.

[0111] Comparative Example 20: The difference between Comparative Example 20 and Example 1 is that the mass ratio of platinum to GaZSM-5 in the mixed solution in step (2) is 0.005:1, the mass ratio of lanthanum to GaZSM-5 is 0.005:1, and the resulting platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst is denoted as 0.5Pt0.5La / GaZSM-5; in the application step, the reaction temperature is 625 ℃.

[0112] Comparative Example 21: The difference between Comparative Example 21 and Example 1 is that the mass ratio of platinum to GaZSM-5 in the mixed solution in step (2) is 0.005:1, the mass ratio of lanthanum to GaZSM-5 is 0.005:1, and the resulting platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst is denoted as 0.5Pt0.5La / GaZSM-5; in the application step, the reaction temperature is 450 ℃.

[0113] Figure 1The X-ray powder diffraction (XRD) spectra of the 0.1Pt0.1La / GaZSM-5 catalyst in Example 1, the 0.5Pt0.5La / GaZSM-5 catalyst in Example 4, the 0.5Pt0.5Y / GaZSM-5 catalyst in Example 14, the 0.5Pt / GaZSM-5 catalyst in Comparative Example 1, the 0.5Pt / ZSM-5 catalyst in Comparative Example 5, and the 0.5Pt0.5La / ZSM-5 catalyst in Comparative Example 6 are shown. It can be seen that all the catalysts exhibit typical characteristic diffraction peaks of ZSM-5 molecular sieves, indicating that ZSM-5 molecular sieves were successfully prepared with high crystallinity. The catalytic materials of Comparative Examples 1, 5, and 6 all exhibited characteristic diffraction peaks of metallic platinum at 39.8°, 46.2°, and 67.5°, while Examples 1, 4, and 14 did not show corresponding characteristic diffraction peaks. This indicates that platinum particles larger than 4 nm appeared in the catalytic materials of Comparative Examples 1, 5, and 6, while the platinum particles in the catalytic materials of Examples 1, 4, and 14 were highly dispersed. No characteristic diffraction peaks of other metals were observed in any of the samples.

[0114] Figures 2-7 The images show transmission electron microscopy (TEM) images of the 0.1Pt0.1La / GaZSM-5 catalyst from Example 1, the 0.5Pt0.5La / GaZSM-5 catalyst from Example 4, the 0.5Pt0.5Y / GaZSM-5 catalyst from Example 14, the 0.5Pt / GaZSM-5 catalyst from Comparative Example 1, the 0.5Pt / ZSM-5 catalyst from Comparative Example 5, and the 0.5Pt0.5La / ZSM-5 catalyst from Comparative Example 6 before reaction. The images show that the catalysts from Comparative Examples 1, 5, and 6 exhibited varying degrees of sintering, characterized by large metal particles, including some with a size >10 nm. Energy dispersive X-ray spectroscopy (EDS) analysis revealed that the large particles in the 0.5Pt / GaZSM-5 catalyst were primarily composed of Pt particles. In contrast, the catalysts from Examples 1, 4, and 11 showed uniformly dispersed metal particles with an average particle size of approximately 1.6 nm, and no large sintered particles were observed.

[0115] Figures 8-11The images show transmission electron microscopy (TEM) images of the 0.5Pt0.5La / GaZSM-5 catalysts from Example 4, Comparative Example 1, Comparative Example 5, and Comparative Example 6 after 12 hours of reaction. The images show that the sintering phenomenon in Comparative Example 1, Comparative Example 5, and Comparative Example 6 was significantly enhanced after the reaction, with the metal particle size increasing compared to before the reaction, and several ultra-large particles larger than 10 nm observed. In contrast, the metal particles in the catalyst of Example 4 remained uniformly dispersed, with an average particle size of 1.6 nm, showing almost no growth, and no large sintered particles appeared.

[0116] Application example: The application of the catalysts prepared in the above embodiments and comparative examples in the propane aromatization reaction includes the following steps: The reaction was carried out in a tubular fixed-bed reactor with an inner diameter of 8 mm; 0.8 g of quartz sand (20-40 mesh) and 0.4 g of platinum-rare earth bicomponent modified GaZSM-5 molecular sieve catalyst 0.1Pt0.1La / GaZSM-5 (pressed into 20-40 mesh particles) obtained in step (2) were uniformly mixed and placed in the constant temperature zone of the reactor. First, N2 (15 mL·min) was added. -1 The temperature was programmed to 550 °C under an atmosphere of ) and then maintained at 550 °C with H2 (15 mL·min). -1 Pretreatment was carried out under N2 atmosphere for 1 h; after pretreatment, the atmosphere was switched to N2 (15 mL·min). -1 After purging the residual hydrogen with an atmosphere, 40 vol% C3H8 / N2 (15 mL·min) was introduced. -1 The reaction was carried out at a temperature of 550℃ and a reaction time of 1.5 h⁻¹. -1 The performance test results of the catalytic material are shown in Table 1 (all data in the table were measured by gas chromatograph after 9 hours of reaction).

[0117] Table 1: Catalytic performance test results

[0118] As can be seen from the table: (1) Compared with the catalysts loaded with a certain amount of rare earth elements, Comparative Example 1 showed lower propane conversion and aromatic selectivity, indicating that the introduction of rare earth elements created more dehydrogenation sites, thereby improving propane conversion. At the same time, the acidity of rare earth metals was weak, which neutralized the strong acidity brought by platinum and gallium sites, further improving aromatic selectivity.

[0119] (2) The catalysts in Comparative Examples 2 and 3, which were not supported on platinum, showed a more significant decrease in propane conversion and aromatic yield compared to Examples 1 and 7, indicating that platinum is an important dehydrogenation active site. In Comparative Example 2, the GaZSM-5 catalyst supported on La had a higher propane conversion rate than the catalyst in Comparative Example 3 without rare earth support, indicating that the introduction of rare earth neutralized the strong acidity brought by gallium sites and further improved aromatic selectivity.

[0120] (3) In Comparative Example 4, the gallium component was loaded by impregnation, but its performance was not as good as that of the framework gallium molecular sieve. This indicates that the gallium species in the impregnated gallium sample are easy to block the molecular sieve pores or agglomerate on the surface of the molecular sieve. The interaction force with the molecular sieve framework is weak, which is not conducive to propane conversion. This further shows that the special coordination environment of the framework gallium species in this invention is conducive to the dehydrogenation and further aromatization of propane. Therefore, it significantly improves the performance of the catalytic material.

[0121] (4) In Comparative Examples 5 and 6, the catalytic materials did not contain gallium, and the propane conversion and aromatic selectivity were significantly reduced, indicating that gallium is a necessary dehydrogenation and aromatization site for the propane aromatization reaction. Comparative Example 7 used ordinary ZSM-5 molecular sieve. Compared with Comparative Example 3, the introduction of gallium into the molecular sieve framework can effectively stabilize acid sites. Gallium also serves as both a Brønsted site and a Lewis acid site in the reaction, thereby improving the propane conversion and aromatic selectivity.

[0122] (5) Comparative Examples 8-9 and Examples 1-7 were loaded with different contents of lanthanum and platinum, respectively. It can be seen that when the lanthanum loading is 0.5 wt% and the platinum loading is 0.5 wt%, the catalytic material has the best reaction performance. Too little lanthanum is not enough to promote the dispersion of platinum, and too much lanthanum will over-neutralize the active sites, resulting in a decrease in catalytic performance. Too little platinum loading does not have enough dehydrogenation sites. Although the excessive platinum has a higher propane conversion rate, it leads to the occurrence of side reactions such as hydrogenolysis, thereby reducing the selectivity of aromatics.

[0123] (6) In Example 8, the gallium source was replaced with gallium chloride. The performance was lower than that of gallium(III) nitrate hydrate as the gallium source under the same metal loading. This is because gallium chloride introduces chloride ions into the system, which are difficult to completely remove during calcination compared to nitrate. The residual chloride ions will poison the metal active sites or change the acidity of the molecular sieve.

[0124] (7) Comparative Example 10 and Example 9 changed the order of gallium introduction during the synthesis process. In Examples 1-7, gallium and aluminum sources were added simultaneously. At this time, gallium and aluminum existed in the solution as tetrahedral coordinated anions, and the two were uniformly mixed at the molecular / ionic level. Gallium basically entered the framework by isomorphous substitution. In Example 9, boehmite was added first and stirred thoroughly before gallium nitrate was added. At this time, aluminum had already reacted with TPA. +A relatively stable structural guiding unit was formed. Gallium, added later, could not undergo uniform condensation during TEOS hydrolysis like aluminum species, and some gallium species struggled to enter the framework. In Comparative Example 10, gallium was introduced after TEOS hydrolysis. At this point, tetraethyl silicate had completely hydrolyzed, and gallium ions easily deposited on the gel surface or entered the pores through electrostatic adsorption, making it difficult for them to enter the framework sites. The resulting catalytic material had a low framework gallium content and an increased non-framework gallium content, weakening its anti-carbon deposition performance and easily causing loss, leading to a rapid decline in reaction performance.

[0125] (8) The calcination temperature and heating rate during the synthesis of GaZSM-5 molecular sieves were controlled in Comparative Examples 11-13 and Example 10. Compared with Examples 1-7, Comparative Example 11 increased the calcination temperature of the crystallized product. At higher temperatures, framework gallium may detach from the framework to form non-framework gallium species, resulting in a reduction of acidic sites. Furthermore, excessively high temperatures may cause partial collapse of the microporous structure, leading to a decrease in the specific surface area and pore volume of the molecular sieve, thus reducing the reaction performance. Compared with Examples 1-7 and Example 10, Comparative Example 12 increased the heating rate of the crystallized product during calcination. An excessively fast heating rate can cause the template agent to rapidly oxidize and decompose in a short time, releasing a large amount of heat and causing partial collapse of the framework structure. Moreover, the water vapor generated by the decomposition of the template agent may cause dealuminization or degaussification at high temperatures, resulting in a reduction of active sites and a decrease in reaction performance. Comparative Example 13 reduced the heating rate of the crystallized product during calcination. An excessively slow heating rate can lead to the accumulation of incompletely oxidized products, which may cause coke residue. In addition, an excessively slow heating rate will significantly increase energy consumption and time costs.

[0126] (9) Comparative Examples 14 and 15 involved stepwise impregnation of platinum and lanthanum species. Compared with co-impregnation, the propane conversion rate decreased to some extent in both cases, with the performance degradation being more pronounced when platinum was loaded first and then lanthanum was loaded. This is because the interaction between platinum and lanthanum is significant in the co-impregnated platinum-lanthanum-loaded catalyst. Lanthanum forms a significant physical barrier to the platinum particles, inhibiting platinum sintering and ensuring uniform dispersion. In contrast, the platinum particles in the catalyst of Comparative Example 14 underwent two calcinations. During the first calcination, there was no rare earth dispersion effect, and the particles had already partially sintered. After the subsequent rare earth impregnation, the interaction between the rare earth and platinum was limited, leading to further sintering of platinum during the second calcination. Similarly, in the catalyst of Comparative Example 15, the interaction between rare earth and platinum was also limited after the subsequent platinum impregnation, resulting in partial sintering of platinum after calcination, thus reducing performance.

[0127] (10) Examples 11-14 used other types of rare earth elements, and their performance was improved compared with the catalyst material without rare earth elements (Comparative Example 1), but the effect was not as good as lanthanum. It is speculated that this is because La 3+The species have moderate ionic radii and strong basicity, which can effectively cover the strong acid sites on the surface of the catalytic material, thereby inhibiting the generation of side reactions and thus improving the anti-carbon deposition performance. Cerium has variable valence, which may promote deep oxidation and dehydrogenation reactions at high temperatures and accelerate the formation of carbon deposition precursors. Praseodymium and neodymium have complex 4f electronic structures, and yttrium has too small ionic radius, which are not conducive to the synergistic effect with the active components.

[0128] (11) In Example 15, the platinum precursor was replaced with tetraammineplatinum(II) nitrate. This precursor is weakly alkaline in aqueous solution. When mixed with rare earth nitrates, the pH value changes, which may cause tetraammineplatinum(II) nitrate to become unstable and decompose. In addition, some rare earth ions are precipitated as hydroxides, resulting in a decrease in loading or uneven dispersion.

[0129] (12) Comparative Examples 16-17 and Examples 16-17 changed the grinding and evaporation temperature of the impregnated product. It can be seen that the propane conversion rate is low when the grinding temperature is below 100°C. This is because the solvent evaporation rate is too slow, which leads to a prolonged metal migration time. Platinum species are severely aggregated on the outside of the molecular sieve crystal, resulting in fewer active sites and rapid deactivation. The performance is even worse when the grinding temperature is above 140°C. This is because chloroplatinic acid decomposes when heated, forming large oxide particles that are difficult to spontaneously reduce into small clusters.

[0130] (13) The heating rate of the impregnated products during calcination was changed in Comparative Examples 18-19 and Example 18. It can be seen that the heating rate of 0.25℃ / min is too slow, and the platinum and lanthanum species are converted into highly stable large-particle Pt with low specific surface area at low temperature. 0 / PtO x It cannot produce a synergistic effect with La2O3. Furthermore, the heating rate of 1.2℃ / min causes the precursor to decompose rapidly, releasing a large amount of gas, which leads to local agglomeration of metal species and a decrease in performance.

[0131] (14) Comparative Examples 20-21 and Examples 19-22 were reacted at different reaction temperatures. It can be seen that the degree of propane activation is low and the conversion rate is low at lower temperatures, while the degree of propane activation is high and the conversion rate is improved at higher temperatures. Comparative Examples 20-21 were reacted at higher and lower reaction temperatures, respectively. At higher reaction temperatures, although the aromatic yield was still high, at 625°C, the catalyst material rapidly carbonized and blocked the pores, covering the active sites, and the molecular sieve was prone to dealuminization, causing the loss of Brønsted acid sites, resulting in a decrease in aromatic selectivity. At too low a reaction temperature, propane activation was difficult, and both propane conversion rate and aromatic selectivity remained at a low level.

[0132] The catalysts obtained in Example 23, Comparative Example 1, Comparative Example 5, and Comparative Example 6 were subjected to a temperature of 550°C for 0.8 h. -1The reaction-regeneration cycle life was tested under space velocity reaction conditions, and the results are as follows: Figures 12-15 As shown. From Figure 12 As can be seen, in the initial stage of the reaction, the propane conversion rate of the catalyst material obtained in Example 23 can reach 98.5%, and the aromatic selectivity remains stable at over 55%. As the reaction proceeds, the single-pass lifetime can reach approximately 120 hours while the aromatic yield remains above 50%. After regeneration, the performance can be restored to the initial level. After 8 cycles of reaction-regeneration, the catalyst remains stable, and the total lifetime can reach over 1000 hours. This indicates that the rare earth metal loading effectively stabilizes the platinum species, thereby improving the stability of the catalyst material.

[0133] from Figure 13 As can be seen from the data, in the initial stage of the reaction, the propane conversion rate of the catalyst material obtained in Comparative Example 1 can reach 98%, and the aromatic selectivity remains stable at over 55%. After two reaction-regeneration cycles, the initial propane conversion rate gradually decreases, and the performance shows a significant decline after about five cycles, or approximately 500 hours. This indicates that pure platinum particles are prone to sintering into large particles, resulting in reduced stability.

[0134] from Figure 14 and Figure 15 As can be seen, the propane conversion rate of the catalysts obtained in Comparative Examples 5 and 6 reached 88% in the initial stage of the reaction, but the propane conversion rate decreased rapidly, and the reaction performance declined significantly after regeneration. This indicates that the synergistic effect of platinum and gallium enhances the activity of acid sites, promotes the aromatization reaction, and the introduction of rare earth metals regulates the acid sites and improves stability.

[0135] It should be noted that the specific implementation methods described above provide a detailed explanation of the technical solution and application results of the present invention. The above embodiments are only the most preferred embodiments and are not intended to limit the present invention. Modifications or equivalent substitutions made by those skilled in the art within the core theoretical scope of the present invention should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a modified GaZSM-5 molecular sieve catalytic material, characterized in that, Includes the following steps: (1) GaZSM-5 molecular sieve was prepared by in-situ hydrothermal crystallization and Ga species were constructed in the ZSM-5 molecular sieve framework; (2) Dissolve the platinum precursor and rare earth precursor in deionized water to obtain a platinum-rare earth precursor solution; (3) Add GaZSM-5 molecular sieve to platinum-rare earth precursor solution, ultrasonically vibrate, grind and evaporate the product, and calcine to obtain platinum-rare earth two-component modified GaZSM-5 molecular sieve catalyst material; the grinding and evaporation conditions are: grind the ultrasonically vibrated product thoroughly at 100~140℃ until it is completely evaporated into a solid; the calcination conditions are: calcinate in air at a rate of 0.5~0.8℃ / min from room temperature to 500~600℃ for 4 h; in the modified GaZSM-5 molecular sieve catalyst material, the platinum loading is 0.1-1.0 wt%, and the rare earth loading is 0.1-1.0 wt%.

2. The method for preparing the modified GaZSM-5 molecular sieve catalytic material according to claim 1, characterized in that, The steps for preparing GaZSM-5 molecular sieve by in-situ hydrothermal crystallization in step (1) are as follows: mix silicon source, aluminum source, gallium source, template agent and deionized water, stir evenly to obtain a mixture; transfer the mixture to a closed reactor for hydrothermal crystallization reaction; after the crystallization reaction, the product is centrifuged, washed and dried, and then calcined in an air atmosphere to obtain GaZSM-5 molecular sieve.

3. The preparation method of the modified GaZSM-5 molecular sieve catalytic material according to claim 2, characterized in that, The silicon source is tetraethyl orthosilicate; the aluminum source is boehmite; the gallium source is gallium nitrate hydrate and / or gallium chloride; the template agent is tetrapropylammonium hydroxide; the molar ratio of silicon source, aluminum source, gallium source, template agent and deionized water is 1:0.01~0.02:0.008~0.009:0.3~0.5:40~50; wherein, the amount of silicon source is SiO2, the amount of aluminum source is Al2O3, and the amount of gallium source is Ga2O3.

4. The method for preparing the modified GaZSM-5 molecular sieve catalytic material according to claim 2 or 3, characterized in that, The hydrothermal crystallization reaction is carried out at a temperature of 170~190℃ for 60~90h. During calcination, the temperature is first increased from room temperature to 350~450℃ at a rate of 1~2℃ / min, and then increased to 500~600℃ at a rate of 0.5~0.8℃ / min for calcination for 4~6h.

5. The method for preparing the modified GaZSM-5 molecular sieve catalytic material according to claim 1, characterized in that, The platinum precursor mentioned in step (2) includes chloroplatinic acid hydrate and / or tetraammineplatinum nitrate; the rare earth precursor includes one or more of lanthanum nitrate hexahydrate, cerium nitrate hexahydrate, praseodymium nitrate hexahydrate, neodymium nitrate hexahydrate, and yttrium nitrate hexahydrate.

6. A modified GaZSM-5 molecular sieve catalytic material, characterized in that, It is prepared by any one of the preparation methods described in claims 1 to 5.

7. An application of the modified GaZSM-5 molecular sieve catalytic material as described in claim 6 in the propane aromatization reaction, characterized in that the method is as follows: the modified GaZSM-5 molecular sieve catalytic material is first pretreated with hydrogen at the reaction temperature, then purged with nitrogen at the same temperature, and then the raw material gas is introduced to carry out the reaction, the reaction temperature is 500~600℃, and the reaction pressure is atmospheric pressure.

8. The application of the modified GaZSM-5 molecular sieve catalytic material according to claim 7 in the propane aromatization reaction, characterized in that, The feed gas is a propane / nitrogen mixture, with the volume content of propane in the mixture being 35-45%.

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